The corrosion inhibition performance, corrosion inhibition efficiency, thermal stability, and chlorine resistance of tolyltriazole and benzotriazole were compared under different pH conditions.

The experimental results showed that tolyltriazole has better corrosion inhibition, thermal stability, and chlorine resistance than benzotriazole. It can replace benzotriazole in the automotive industry and water treatment industry.

Benzenetriazole, molecular formula C6H5N3, molecular weight 119.1, colorless or light yellow needle-like crystals.

Since benzotriazole can form covalent and coordination bonds with copper atoms, they alternate with each other to form a chain-like polymer. It forms a multilayer protective film on the surface of copper so that the surface of copper does not have an oxidation-reduction reaction. Thus, it acts as a corrosion inhibitor. Benzenetriazole can be used as a corrosion inhibitor for copper and copper alloy equipment.

Benzotriazole also has an anti-corrosion effect on aluminum, nickel, zinc, and other metal materials.

Benzotriazole is used in cooling water treatment, air conditioning water treatment, and especially in closed circuit water circulation systems. It can be used with a variety of corrosion inhibitors such as polyphosphates, molybdate, silicates, nitrites, ATMP, HEDP, etc. to improve its corrosion inhibition efficiency. Benzotriazole can also be used in automotive antifreeze, brake fluid, and cutting fluid for metal processing.

Tolyltriazole, molecular formula C7H7N3, molecular weight 133.16, has the appearance of light yellow granules or powder.

Tolyltriazole is a kind of metal protective agent. It can form a protective film on the surface of copper and can make copper ions sink from the solution. Thus, it plays a role in preventing galvanic corrosion on metal.

Tolyltriazole has better corrosion inhibition, oxidation resistance, and high-temperature resistance as well as long-term storage performance than benzotriazole. It can be widely used as a substitute for benzotriazole in lubricants, metal working fluids, cutting fluids, antifreeze, brake fluids, circulating cooling water systems, etc.

Comparison of the properties of Tolyltriazole and benzotriazole

1. Comparison of corrosion inhibition performance

The stability of copper corrosion inhibitors is particularly important in systems containing aluminum. The pitting of aluminum is caused by the precipitation of copper ions.

By conducting separate corrosion protection experiments with tolyltriazole and benzotriazole in automotive antifreeze products. The different corrosion inhibition performance of the two in the presence of aluminum was compared. Table-1 indicates the weight loss of metals in corrosion experiments.

Table-1. Weight loss of test pieces in two types of corrosion inhibitors, mg/piece
Corrosion InhibitorsWeight Loss
Soldering tinBrassPurple CopperCast AluminumCarbon SteelCast Iron

2. Corrosion inhibition efficiency under different pH environments

The data in Table-2 record the amount of corrosion inhibitor required to achieve 95% or higher corrosion inhibition efficiency.

Table-2. Corrosion Inhibitor Dosage When Corrosion Inhibition Efficiency ≥ 95%, ppm
pH ValueTolyltriazoleBenzotriazole

The above results show that tolyltriazole apparently has less dosage and higher corrosion inhibition efficiency than benzotriazole.

3. Thermal stability experiments

The same percentage of tolyltriazole or benzotriazole was added to the two antifreezes. After 88±2°C, 336h experiments, the remaining content of tolyltriazole or benzotriazole in the respective antifreeze was analyzed every two days. This was used to evaluate their respective thermal stability. The results of the experiments are shown in Table-3.

Table-3. Residual Content of Tolyltriazole and Benzotriazole in Antifreeze with Time, %
Time/dayCorrosion Inhibitor Content

4. Chlorine resistance

Specimen sets consisting of copper and aluminum were placed into the solution at a solution temperature of 50°C, an initial pH of 8.0, and different chloride ion concentrations. A 24h corrosion experiment was conducted.

This experiment tested the corrosion inhibition efficiency of copper by methylbenzotriazole and benzotriazole at different chloride ion concentrations and in the presence of aluminum.

At the same time, the relationship between different corrosion inhibitor concentrations and corrosion inhibition efficiency was also tested under the condition of a certain chloride ion concentration. The specific experimental results are shown in Table-4 and Table-5.

Table-4. Inhibition Efficiency of Benzazole and Tolyltriazole Against Copper at Different Chloride Concentration, %
Chloride ion concentration, ppmInhibition Efficiency
Table-5. Relationship between corrosion inhibition efficiency and concentration of inhibitor, %
Chloride ion concentration, mg/LInhibition Efficiency


Compared with benzotriazole, tolyltriazole has better corrosion inhibition, thermal stability, and chlorine resistance. Tolyltriazole can replace benzotriazole in the automotive industry and water treatment industries.